# O. Ostrovska

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Articles: 2

### Unitary representations of Poincaré group ${\mathrm{P}(1,n)}$ in ${\mathrm{SO}(1,n)}$-basis

Methods Funct. Anal. Topology 27 (2021), no. 3, 258-276

This paper concerns the problem of reduction of unitary irreducible representations of the Poincaré group $\mathrm{P}(1,n)$ with respect to representations of its subgroup $\mathrm{SO}(1,n)$. Based on a generalization of the Wigner-Eckart theorem, we obtain matrix elements of the shift operators in the $\mathrm{SO}(1,n)$-basis.

Робота присвячена проблемі редукції унітарних незвідних представлень групи Пуанкаре $P(1, n)$ відносно представлень її підгрупи $SO(1, n)$. На основі узагальнення теореми Вігнера-Еккарта отримано матричні елементи операторів зсуву в $SO(1, n)$-базисі.

### On isometries satisfying deformed commutation relations

Methods Funct. Anal. Topology 25 (2019), no. 2, 152-160

We consider an $C^*$-algebra $\mathcal{E}_{1,n}^q$, $q\le 1$, generated by isometries satisfying $q$-deformed commutation relations. For the case $|q|<1$, we prove that $\mathcal E_{1,n}^q \simeq\mathcal E_{1,n}^0=\mathcal O_{n+1}^0$. For $|q|=1$ we show that $\mathcal E_{1,n}^q$ is nuclear and prove that its Fock representation is faithul. In this case we also discuss the representation theory, in particular construct a commutative model for representations.